Here is the problem. When Vastu Shastra was written, wall clocks were not invented. So you don’t have any prescription as per Vastu Shastra. If you put it anywhere as per your choice, it may bring harm. You cannot be sure. The best thing is to keep it on your head.

With a screen name like rishi you should not be believing in Vaastu.
Put it where it looks best. Or as Groucho Marx remarked when he hit his head on a wall clock at his friend’s house,’Why don’t you wear a watch like everyone else?’